Javascript Find char in string reverse from position

find_in_string_reverse.js

if (typeof String.prototype.findACharInStringPrev !== 'function') {
    String.prototype.findACharInStringPrev = function(char, start) {
    	do {
    		if(this[start] == char)
    			return start;
    		start--;
    	}while(start >= 0)
    	return -1;
    };
}